Geared Four-Bar Mechanisms

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Geared Four-Bar Mechanisms

Geared Four-Bar Mechanisms

Geared Four-bar Mechanisms are usually assembled with:

A four-bar mechanism - with at least one Part that rotates continuously

One or two Gear-Pairs

The input 'drive' gear is fixed to the Coupler, at the distal end of the Crank or the Rocker

The output gear is usually at the joint with the Base-Part of the respective Crank or the Rocker

Geared Four-Bar Mechanisms are often used as 'Function-Generators'. Function-Generators provide an input to output mathematical relationship.

Geared Four-bar Mechanism Configurations

One Gear-Pair

Regressive and Ir-regressive Gears. (I do not know why they are called regressive and ir-regressive gears).

Regressive gears - a gear at each end of the Crank of a four-bar.

Ir-regressive gears - a gear at each end of the Rocker of a four-bar.

Note: A 'Four-bar' is a common term for a 'kinematic-chain with four Parts' usually with four Pin-Joints, usually one Part is the Base-Part.

Regressive Geared Four-bar

GST-T14-Regressive-A

STEP 1: A Four-bar


Line-of-Centers

The Line-of-Centers for the Regressive Gear-Pair is the CAD-Line in the Crank.

The input to the Regressive Gear-Pair is the Coupler.

The output from the Regressive Gear-Pair, is the Geared-Rocker. It is a new Part.

The rotating axis of the Geared-Rocker (new Part)is at the rotating-axis of the Crank

 

GST-T14-Regressive-C

STEP 2: Add the rotating-Part for the output of the Regressive Gear-Pair

1.Kinematic toolbar > Add Part

2.Kinematic toolbar > Add Pin-Joint

a.Click the start-Point of the new Part

b.Click the Origin of the Crank

There are two Points at the origin of the Crank - the start-Point of the Crank, and the start-Point of the Line in the Base-Part.

GST-T14-Regressive-B

 

The Select-Elements dialog opens because you have clicked three Points in total

STEP 2: Select two Points in the Select-Elements dialog-box

1. CTRL+Click the start-Point of the new Part (Part4)

+

2.CTRL+Click the start-Point of the Crank (Part)

3.Click OK-tiny-13-17 to close the Select-Elements dialog-box

Why select the start-Point of the Crank?

The Line-of-Center is the CAD-Line in the Crank. The Pin-Joints be with Points at each end of the Line-of-Center.

GST-T14-Regressive-D

STEP 4: Add the Regressive Gear-Pair

1.Click Machine elements toolbar > Add Gear-Pair

2.Click the CAD-Line in the Coupler

3.Click the Cad-Line in the new free Part

4.Click the CAD-Line in the Crank

5.Click the dimension Line that defines the length of the Crank

6.Click OK-tiny-13-17 in the Command-Manager

GST-T14-Regressive-E

STEP 5: Edit the Gear-Pair

If you do not want to change the length of the Crank, do not change the total number-of-teeth.

STEP 6: Plot a Graph of the Output vs the Rotation of the Crank

Add a Measurement FB to measure the motion of the Geared Rocker - the Output-Gear

Add a Graph FB

GST-T14-Regressive-F

GST-T14-Regressive-G

'Ir-regressive' Geared Four-bar

GST-T14-Regressive-A

STEP 1: A Four-bar

Line-of-Centers

The Line-of-Centers for the Regressive Gear-Pair is the CAD-Line in the Crank.

The input to the Regressive Gear-Pair is the Coupler.

The output from the Regressive Gear-Pair, is the Geared-Rocker. It is a new Part.

The rotating axis of the Geared-Rocker (new Part)is at the rotating-axis of the Crank

GST-T14-IRRegressive-A

STEP 2: Add the rotating-Part for the output of the IR-Regressive Gear-Pair

1.Kinematic toolbar > Add Part

2.Kinematic toolbar > Add Pin-Joint

a.Click the start-Point of the new Part

b.Click the Origin of the Rocker

There are two Points at the origin of the Rocker - the start-Point of the Rocker, and the end-Point of the Line in the Base-Part.

GST-T14-Regressive-B

The Select-Elements dialog opens because you have clicked three Points in total

STEP 3: Select two Points in the Select-Elements dialog-box

1. CTRL+Click the start-Point of the new Part (Part4)

+

2.CTRL+Click the start-Point of the Rocker (Part)

3.Click OK-tiny-13-17 to close the Select-Elements dialog-box

Why select the start-Point of the Rocker?

The Line-of-Center is the CAD-Line in the Rocker. The Pin-Joints be with Points at each end of the Line-of-Center.

GST-T14-IRRegressive-B

STEP 4: Add the Regressive Gear-Pair

1.Click Machine elements toolbar > Add Gear-Pair

2.Click the CAD-Line in the Coupler

3.Click the Cad-Line in the new free Part

4.Click the CAD-Line in the Crank

5.Click the dimension Line that defines the length of the Crank

6.Click OK-tiny-13-17 in the Command-Manager

GST-T14-IRRegressive-C

STEP 5: Edit the Gear-Pair

If you do not want to change the length of the Crank, do not change the total number-of-teeth.

STEP 6: Plot a Graph of the Output vs the Rotation of the Crank

Add a Measurement FB to measure the motion of the Geared Rocker - the Output-Gear

Add a Graph FB

GST-T14-IRRegressive-D

 

GST-T14-IRRegressive-E